I figured it might be a good time to post this. Here is a thread on my one and only Germlang:Sperenjas Razzo
This post is just meant to give a short overview of the language with its different stages and general properties.

1. Diachronic Phonology
This section supplies a summary of the phonological changes and the phonological inventory at different stages.

Phonological changes from Proto-Germanic to Proto-Sperenjas The most interesting things going on this period are massive fricative mergers, strict monophthongization and loss of labiovelars. Also word-final nasals are strengthened, a unique feature of this lang (AFAIK).

Phonological changes from Proto-Sperenjas to Late Proto-Sperenjas
The length distinction in vowel is changed into a tenseness distinction. Also some changes in fricatives.

Spoiler:

ɣ→j
x→h
V[+tense] → V[-tense] !_ː
ː→∅
jj→j

Late Proto Sperenjas Segmental Inventory

Spoiler:

/m n ŋ/
/p t k/
/b d g/
/f s h/
/v z/
/r l j w/

/ɪ i ʏ ʊ u/
/ɛ e œ ø ɔ o/
/ɐ a/

Phonological changes from Late Proto-Sperenjas to Early Old Sperenjas
Front rounded vowels are lost and lax high vowels merge with tense mid vowels. Some consonant clusters are reduced and /h/ is deleted, triggering compensatory lengthening whenever possible.

Phonological changes from Early Old Sperenjas to Old Sperenjas
There is fortition of /w/ to /v/ and mid lax vowels merge with mid tense vowels.

Spoiler:

ɛ→e
ɔ→o
w→v

Old Sperenjas Segmental Inventory

Spoiler:

/m n ŋ/
/p t k/
/b d g/
/f s/
/v z/
/r l j/

/i u/
/e ə o/
/a/

Phonological changes from Old Sperenjas to Late Old Sperenjas
/j/ is deleted between non-round vowels, the emerging vowel sequences result in long vowels. The length distinction is further elaborated by shortening unstressed long vowels and lengthening stressed vowels in open syllables. Stress is assumed to be on the first syllable.

Phonological changes from Late Old Sperenjas to Very Early Middle Sperenjas
There is Schwa deletion in several contexts and some of the resulting consonant clusters fuse. Word final devoicing takes place for obstruents.

Spoiler:

ə→∅/VC_C#
ə→∅/VC_CV
ə→∅/VC_#
ə→∅/#_CV
ə→∅/#C_CV

nm→m
mn→n
nŋ→ŋ
ŋn→n
ŋm→m

C[-sonorant,+voice]→C[-sonorant,-voice]/_#

Phonological changes from Very Early Middle Sperenjas to Early Middle Sperenjas
Front vowels become allophonically rounded before labial consonants. Dorsal and coronal obstruents become undergo palatalization before /j/ and the high front vowel.

Phonological changes from Early Middle Sperenjas to Middle Sperenjas
Front rounded vowels are backed and the schwa undergoes some kind of vowel assimilation. Unstressed vowels are centralized.

Spoiler:

V[-back,+round]→V[+back,+round]

ə→e/_(C)(C)(C){e,i}
ə→o/_(C)(C)(C){o,u}

i→ɘ/VC(C)(C)(C)_
e→ɜ/VC(C)(C)(C)_
o→ɞ/VC(C)(C)(C)_
u→ɵ/VC(C)(C)(C)_

Middle Sperenjas Segmental Inventory

Spoiler:

/m n ŋ/
/p t ʦ k/
/b d ʣ g/
/f s ʃ/
/v z ʒ/
/r l j/

/i iː u uː/
/e eː ɜ ɘ ə ɞ ɵ o oː/
/a aː/

Phonological changes from Middle Sperenjas to Late Middle Sperenjas
Centralised vowels merge into schwa and voiced fricatives become plosives after nasals.

Spoiler:

ɘ→ ə
ɜ→ ə
ɞ→ ə
ɵ→ ə
v→b/N_
z→d/N_
j→g/N_

Late Middle Sperenjas Segmental Inventory

Spoiler:

/m n ŋ/
/p t ʦ k/
/b d ʣ g/
/f s ʃ/
/v z ʒ/
/r l j/

/i iː u uː/
/e eː ə o oː/
/a aː/

2. Orthography
I will use the following romanization conventions for Old and Middle Sperenjas. Sometimes I will use a romanization based on an older stage for etymological reasons. Stress is not indicated.
/ə/ <a>
/Vː/<VV>
/ŋ/ <ng>
/ʦ/ <tj>
/ʣ/ <dj>
/ʃ/ <sj>
/ʒ/ <zj>

3. MorphologyConjugations
Sperenjas only distinguishes past and non-past forms of all verbs from a very early stage. Dual forms were also lost. It keeps however most of the conjugation classes, except for those, that became indistinguishable due to phonological changes. The infinitive is marked with -<ang>, some forms of the language also use a present participle.The following examples instantiate three different conjugations in Old Sperenja: the first strong conjugation, the first weak conjugation and the present-preterite.

Declension
Sperenja lost the nominative singular marker -<az> very early on, and similar nominative singukar suffixes were lost in analogy. Often the vocative singular form was substituted. Pronouns and article show special declension different from regular nouns. However, only four cases were kept, some of them merging in certain paradigms. Here are three examples from the a-declension of Old Sperenja with a masculine, feminine and neuter noun.

4. Syntax
Syntax is usually SOV, with a relatively free word order in the noun phrase. The default position for articles and possessors is in front of the noun, whereas adjectives often follow the noun. Object clitics in Middle Serenja precede the verb. The same position is taken by certain sentential clitics.

5. Vocabulary
Here is a list of vocabulary for Middle Sperenjas. Note the threefold distinction in motion verbs based on the direction and the locative copula which is cognate to English 'to lie'.

geevanang - *gebaną - to give, to transfer (has to be a completed action)
geevenang - to take (has to be a completed action)
geevare - someone who gives something (has to be a completed action)
saljanang - *saljaną - to give, to offer (usually only the intention to give something)
saljenang - to take (usually only the intention to take something)
saljare - someone who offers something

Apart from the usual begging for feedback, I want to ask a specific question. Since the next step will be importing loan words from latin at several stages, I would like to know the following: How long do you think would the sound changes take? When would Old Sperenja and Middle Sperenja be spoken?